Isolated data/power transfer with reinforced galvanic isolation has attracted continuing development based on various approaches.
A possible approach may involve e.g. integrated high-voltage capacitors. Based on that approach, capacitors may be integrated with a thick isolating layer (e.g. SiO2) to achieve galvanic isolation. Isolation rating values higher than 5 kV may involve both technological and cost issues; these may be penalizing in terms of larger area due to a lower capacitance density. Also, in certain implementations only data transfer (and no power transfer) may be achieved while common-mode transient immunity (dV/dt) may become a critical factor due to high capacitive coupling.
Another approach may involve post-processed isolation transformers, possibly using polyimide isolation layers. Isolation rating values higher than 5 kV may be achieved with thick layers (e.g. >20 micron) at the cost of a lower magnetic coupling. Transfer of both data and power may be available e.g. with different transformer links.
Still another approach may involve integrated isolation transformers, e.g. fully integrated e.g. in standard Si technologies (e.g. BCD). Isolation rating values up to 5 kV may be obtained with e.g. thick SiO2 layers for instance between MTL4-MTL3. Isolation rating values up to 6 kV can be achieved by exploiting lower metal layers, as well. Transfer of both data and power may be available on a same transformer link. Reinforced isolation is hardly achievable due to limitations in oxide thickness.
Still further approaches may involve increasing the isolation rating by series-coupled isolation devices. For instance, series capacitors or transformers may be exploited to improve the isolation rating (possibly by doubling it) without increasing the isolation layer thickness. In such implementations, data transfer may be implemented while high losses due to series isolation transformers may prevent effective power transfer.
Despite the extensive activity in that area, a demand is still felt for improved galvanic isolation arrangements.